Vats, drums, dyes, acids, formulas, paints, powders, bobbins, ovens, molds and boilers - not things you'd normally expect to see in Southern California, even on a factory tour. And while zippers were invented by an American, it's easy to assume they stopped being "made in the USA" decades ago.

But U-Can Zippers has been at it on Long Beach Avenue for 25 years, and despite the manufacturing exodus to cheaper labor markets overseas, this family business has no intention of going anywhere.

Today Hyrum Lai, 35, is playing tour guide. Visitors are always welcome at the factory, although Tuesdays and Thursdays are the best days to drop by. Lai says that he's just given a walk-through to some fashion and design students from the nearby Fashion Institute of Design & Merchandising: "They'll be sourcing these zippers in the future, and need to know what's involved. A zipper is just a zipper to anyone else, but they have so many different functions that it can run into problems."

He explains, "People think it's easy, call us last and expect it overnight, but it can take several weeks." For example: "The exposed zipper is big right now, and designers want one on the yoke" - aka shoulders - "that joins together, then zips down the back, but doesn't zip all the way closed. So we have to work out how to connect four different zippers."

Zippers, it turns out, are complicated. Stored upstairs are rows of ceiling-high shelves filled with "overruns," massively long chain lengths of zippers, with or without their teeth already in them. One end hangs down so customers can choose the color. It's like a giant's swatch book, carefully color-coordinated lengths hanging down like streamers as far as you can see.

Later Lai walks past shelves of bagged overrun sliders, the official name for the thing you slide up and down the zip. They come in all colors, shapes and sizes. Along with your choice of slider, color and pull (the tiny tab on the slider that you actually hold), U-Can needs to know the width of the teeth and if you want "classic" flat wire, "alpha" pre-formed, or the most expensive, "G2," which has gold or copper plating and costs $6 a yard.

There's more. Nylon coil, plastic mold, metal or reverse; pieces or long chain; brass base wire or something more expensive? Will you have a bottom stop, or a pin and box? The list goes on, and "sometimes even the most common color, black, isn't black," Lai laughs.

He laughs a lot during the tour, explaining, "The look in people's eyes when I show them around reminds me this is a pretty cool and unusual place."

It wasn't always that way, as he and his older brother Malan Lai, 38, recall later in their office. Of their years working in the factory during summer vacations, "We both hated it, and we also thought, 'Who cares about zippers?'?" Hyrum Lai says. "I was in advertising out of school and I always swore I'd never work here."

His older brother adds, "When we were teenagers we were very anti-zipper, and deliberately bought clothes with Velcro or buttons!"

When the brothers were young adults, however, their parents left for Hong Kong to do volunteer work for their church, and Hyrum was asked to start helping his "heir apparent" brother run the factory. "It was supposed to be for a year and a half, and now it's nine years later," Hyrum Lai shrugs, admitting that while he can more or less identify zippers by sight, he's still learning an industry that shies from standardization.

The factory has the air of a World War II munitions factory, with the clangs of chopping, steaming, banging, shaking and even what sounds like a machine gun. There are rolls of material and countless odd-looking machines with various types of zippers trundling, winding or shooting in or out of them. Oh, and what looks like a nuclear reactor at the back.

Even what looks like an empty box is the light box, a device that allows workers to check how a zipper looks in various lights - say, the default (gray-blue, midday noon), or perhaps Target's choice of T30, a bright light matching the lighting in its stores. To its left is a small room for mixing powder for dyes, and beside that is the lab, where the Spectrometer breaks down the components of a customer's fabric swatch before a small sample dye is mixed from the powders, approved, then readjusted for the full run.

It's a little overwhelming, though the lab's mixing machine brings to mind something familiar from the movies. "The kids from FIDM say, 'This is so Frankenstein,'?" Hyrum Lai says of the glass-fronted cabinet, which has numbered, old-style glass jugs filled with spiraling tubes and leading into a whirling wheel device that mixes the color elements.

A worker on the job at U-Can

Photo by Danny Liao

On the floor, the noise continues: There are boilers that use pressure and temperature to dye white polyester, and circular "hoppers" that use small jets of air and vibrations to jog pins and boxes around a carousel and bring them together.

A paint-splattered table is lined with pots of dazzlingly bright enamel primary colors. Here a gas-masked worker named Antonio loads up the washing machine - like tumble cages with sliders, and then adds the chosen color to be sprayed on. "He mixes them by eyeball," Hyrum Lai says. "It's an amazing talent."

Back in the office, the boys' mother, Liz, arrives, followed quickly by father Paul in his wheelchair. Paul Lai is still a regular visitor. "After 25 years," he says, "the overseas contacts expect me. ... I'm not a CEO, I'm a CKO - Chief Knowledge Officer."

The Taiwanese-born Paul Lai had been working in fast food - originally, "I flipped the burger!" he laughs - when a Taiwanese company called Zipper Power approached him to run the factory back in 1984. The plan had been to set up in New York, but he found it "too far and too cold!"

In the early years business boomed. U-Can ran 24/7 six days a week and had 200 employees, even with no sales force. "But then China opened, and people could buy their own inexpensive machinery," Paul Lai says. "I focused on how we can maintain without moving to China but still respond timely to Eastern USA, the fashion center."

The factory now employs 43 people, and Japanese behemoth YKK controls 90 percent of the world market. It's even bought the company that supplies most zipper machines. U-Can is the only remaining U.S. zipper company west of the Mississippi.

Paul Lai is convinced that its larger competitor wants U-Can dead. "But one mean tiger cannot kill thousands of monkeys. He might kill 50, but not all of them. We're still here."

Says Hyrum Lai, "While we're too small for YKK to bother with us, I know we're a thorn in their side. But if they came knocking, I wouldn't show them around."

U-Can ships all over the United States, and occasionally Japanese companies will import its zippers because their customers love anything American.

Take a look at your own zipper and you might see it's stamped with U-Can or another maker's initials, although sometimes customers want their own design there (or none at all).

U-Can sold between 2 million and 3 million zippers in 2013 - one of its best years. And though they've kicked around ideas about diversifying into buttons or going more digital, the family will probably stick at what it's best at. Malan Lai says, "When my father first purchased this business, he said he was flying on a trip and all he heard around him was zip, zip, zip, zip, and he thought, 'If I can't make it in this business...'?"

His brother relates one more story. "In 1993 we were on vacation in Hawaii, and were in a department store," he says. "I was looking through the clothes, and then I saw one of our U-Can zippers."

Paul Lai finishes the anecdote: "And he held it up and went, 'Dad! Look!'?"

Editor's note: The original headline on this story misstated the location of U-Can's Long Beach Avenue factory. It is in Vernon. We regret the error.